Internal combustion engines such as diesel engines, gasoline engines, and gaseous fuel-powered engines combust a mixture of fuel and air to generate a mechanical power output that can be used in many different ways for a variety of purposes. Unfortunately, conventional engines are inefficient, and much of the energy of the fuel is wasted in the form of heat. For example, heat can be generated during compression of combustion air directed into the engine or during pumping of fluids (e.g., fuel, air, lubricant, etc.) through the engine. Additional heat is generated directly from combustion of the fuel and air, and is transferred to the engine block and to fluids (oil, coolant, exhaust, etc.) circulating through the block. Most of this heat energy is eventually discharged or otherwise dissipated to the environment.
In addition to efficiency losses associated with heat waste, extra energy must be expended to protect components of the engine from the heat and/or to keep performance of the engine from declining due to the heat. For example, the inlet air must be chilled, jacket water coolant must be circulated through the engine block, engine oil must be cooled, and exhaust temperatures may need to be lowered in order to adequately protect the engine and/or to ensure desired performance. Each of these actions requires extra energy, which reduces the mechanical power output of the engine and further lowers its efficiency.
In gaseous-fuel powered engines, for example natural gas or dual fuel (natural gas and diesel) engines, some or all of the fuel may be stored in liquid form at very cold temperatures. The liquid must be heated to a state of vaporization prior to combustion inside the engines. This heating requires additional energy, which can further lower the efficiency of the engine.
One attempt to improve the efficiency of a gaseous fuel powered engine is disclosed in U.S. Pat. No. 7,360,368 of Fickel et al. that issued on Apr. 22, 2008 (“the '368 patent”). Specifically, the '368 patent discloses an engine that combusts fuel drawn from a cryogenic fuel tank. The engine has an exhaust gas recycling device, and a radiator coupled to chill fluid directed through an engine coolant circuit to the exhaust gas recycling device. The engine also has a vaporizer coupled to the fuel tank via a fuel heating circuit. The engine coolant and fuel heating circuits are thermally connected to each other via a heat exchanger, such that heat from the exhaust gas recirculation device is used to vaporize fuel in the vaporizer prior to consumption of the fuel by the engine.
Although the engine of the '368 patent may have improved efficiency through the dissipation of heat from the exhaust gas recycling device to the vaporizer, it may still be less than optimal. In particular, because the exhaust gas recycling device is thermally connected to the engine coolant circuit, in addition to the fuel heating circuit, it may be difficult to control either the temperature of the exhaust gas recycling device or the fuel.
The disclosed power system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.